Electrical transmission and distribution circuits include conductors supported by grounded support structures such as wooden poles, steel poles, concrete poles, and lattice towers. The support structures are essentially grounded since they are embedded in the earth. Each conductor (or wire) is separated from the grounded structure by an insulator, such as a ceramic insulator. The insulators also provide separation between the conductors (or phases). The phase separation is determined by the circuit voltage, the proximity to ground, and the length of the span.
Insulators are manufactured in various sizes and shapes according to industry standards. The insulator chosen for use on a support structure varies in size and is dependent on the circuit voltage as well as other electrical and physical characteristics.
The construction and design of support structures vary for single phase and three phase electrical circuits. The insulators and phases attached to a crossarm or supporting member may all be at the same level horizontally and separated a certain distance according to industry standards. Or, they may be configured vertically and attached to the support structure by means of a bracket or supporting member.
The distance between the insulators, energized phases, and ground potential varies according to the circuit voltage and other characteristics. If a bird, squirrel, or other animal perched or sitting on a support structure, supporting member, conductor, or insulator completes a circuit phase to phase, or phase to ground, a flashover will occur, resulting in an outage, disrupting power to customers, and the death of the animal.
Electricity is always seeking a path to ground. Therefore, industry guidelines recommend that energized conductors have adequate separation phase to phase and phase to ground. This separation is referred to as clearance. Electricity flows over the surface of a conductor or insulator. With regards to insulators, the separation or surface area between the conductor and ground is referred to as leakage distance. Typically, insulators are manufactured with skirts to lengthen the surface distance phase to ground and minimize the overall height of the insulator. If an animal approaches the energized conductor or insulator and provides a conductive path to ground, or if an animal effectively reduces the necessary separation or clearance of two energized conductors, a short will occur in the circuit, resulting in a momentary or permanent outage. Depending on the circuit voltage, this animal does not necessarily have to come in direct contact with the energized conductor or insulator for the electricity to discharge across to the conductive path. Mylar balloons have also been known to create the short circuit. Additionally, the shorting could also be caused by an improperly installed or damaged wildlife deterrent device installed by a lineman with insufficient clearance from the energized conductors and insulators. It is essential that adequate separation or clearance be maintained phase to ground and phase to phase.
The present invention relates to an improved wildlife deterrent for use on a high voltage utility support structure, such those generally used to support electrical distribution conductors between substations and homes or businesses. The conductors typically carry AC voltages under 75 kV and as little as 120 V. Such supporting structures may have multiple supporting members, where the highest supporting member supports conductors carrying the highest voltage. Medium to high voltage conductors are frequently not shielded by insulation.
Some wildlife deterrents are known. One type of deterrent is a preformed plastic triangle that is bolted to the support member between two conductors, where the closest distance between a triangle arm and a conductor is insufficient to cause a flashover through the plastic but close enough to prevent an animal going between the conductor and the triangle. However, although rigidly-shaped deterrents may be suitable for some insulator spacings, the same deterrent may not be suitable for a range of insulator spacings. Therefore, different sizes of such deterrents must be on hand for the lineman, or a compromise must be made by using the single deterrent for different situations.
An adjustable-angle deterrent is manufactured by Hendrix Conductor & Cable, Inc. that consists of two arms attached at a pivot point. The arms are spread to provide the desired distance between each arm and its closest conductor, while not leaving room for an animal to perch between the arm and the conductor, and the free ends of the arms are nailed or lagged to the supporting member to form a triangle. However, with such a deterrent, the angle becomes less and less as the arms are spread wider and wider to accommodate different spacings of conductors. This design cannot be used on metal or concrete type supporting structures due to the method of nailing or lagging. Therefore, there must be a compromise between: 1) the closest space between the deterrent and the conductor to deter wildlife yet avoid flashover between the conductor and the deterrent; and 2) the angle of the arms, where a steep angle of the arms is needed to deter animals perching on the arms.
Another type of wildlife deterrent, manufactured by Midsun Group, Inc., has a fixed-length vertical rod and two sets of three pivoting arms extending from opposite sides of the vertical rod. The six arms prevent a bird from roosting on the support member, provided the insulators and conductors are spaced adequately from the arms of the deterrent. If the insulators and conductors are spaced beyond the maximum width of the deterrent and there is too much clearance between the deterrent and the insulator, the deterrent becomes ineffective. Further, as the arms are spread out and become more horizontal to widen the overall design of the deterrent, the arms do not maintain the angle needed to discourage a bird from landing on them. The deterrent effectively becomes an inviting perch instead of a deterrent to perch.
Conversely, if the insulators are spaced close together, the deterrent may jeopardize the phase to phase spacing.
What is needed is an adjustable wildlife deterrent for utility support structures that can be easily and quickly configured by the lineman for optimal deterrence by maintaining critical angles to discourage birds and wildlife from perching and sitting next to energized conductors and insulators and provide the necessary adjustability for clearance issues to prevent flashover from occurring phase to ground, phase to phase, with varying conductor and insulator spacings.